He is the Ubiquitous. He is the Unknown. He is, as one observer put it, "the holograph; the metaphor."

He is Bruce Willis, and if he doesn't think of himself as a holograph or metaphor, well, that would be weird, since he was the observer who said that of himself (in a recent Vanity Fair article).

BRUCE ALMIGHTY - Bruce Willis returns to his signature role as tough cop John McClane in 'Live Free or Die Hard.' CNS Photo courtesy of 20th Century Fox.

He has also been called the "fly in the ointment, the monkey in the wrench. The pain in the (rear end)."

That was, again, Willis, exhibiting his trademark flair for vivid quips even as he displayed a somewhat fuzzy grasp of the role actual monkeys play in adages about wrenches.

To be more precise, that was John McClane - Willis' tough-cop character in the "Die Hard" movies - talking about John McClane in the original 1988 film. McClane, who makes his triumphant return in the fourth movie, "Live Free or Die Hard," is easily Willis' signature role.

It's been 12 years since McClane last hit the screen, in the memorably titled "Die Hard 3: Look Who's Dying Hard, Too!" Although it's possible we're mixing that up with another of Willis' famous franchises.

Though he first made it big on TV, in the '80s series "Moonlighting," Willis has been a movie star for a couple of decades, playing action heroes ("Armageddon," "The Last Boy Scout") and sensitive types ("The Story of Us") and more action heroes ("The Fifth Element," "Tears of the Sun," "Pulp Fiction") and even, in "The Sixth Sense," a guy who is dea ... uh, has some health issues. In all, he has more than 70 acting credits on screen and TV. In "Live Free or Die Hard," Willis plays a reluctant hero who smites scads of heavily armed terrorists using only his wits, a cigarette lighter and a scintillating bon mot or two.

In that respect, he is like the Martha Stewart of action heroes. Except that Martha prefers salt in her paella, while Willis puts it in his conversation. His most famous "Die Hard" line is "Yippee-ki-yay, (sucker)," only with a different, somewhat longer word at the end.

(Bonus Web tip: See Willis utter the secret word on live TV - oops! - at YouTube.com. While there, also check out the random guy playing the original composition "The Ballad of John McClane" on acoustic guitar.)

"Live Free or Die Hard" plays off the New Hampshire state creed, which hints at possible motto-based movies to come: for Kentucky, "United We Stand, Divided We Fall, Hard We Die"; or for Hawaii, "Ua Mau Ke Ea O Ka Aina I Ka Pono, (Sucker)."

The way Willis - the man, the metaphor, the flying monkey in the holographic ointment - continues to flay bad guys and work that smirk, you can bet the "Die Hard" franchise isn't going to die soon, hard or otherwise.

And to that, the only proper response is: Yippee-ki ... yay?

Whatchoo talkin' 'bout, Willis?

A sampling of La Bruce's words of on-screen wisdom:

- "Boy, are you a tough customer. I bet you didn't even clap your hands to save Tinker Bell." (To Cybill Shepherd, his co-star in "Moonlighting.")

- "Help! Help! Somebody burp me before I blow up!" (In "Look Who's Talking," the first of his chatty-baby comedies.) - "This is the '90s. You don't just go around punching people. You have to say something cool first." (Getting all postmod in "The Last Boy Scout.")

- "The United States government just asked us to save the world. Anyone wanna say no?" (Getting patriotic in the asteroid-based drama "Armageddon.")

- "All I see are dead people." (Visiting the past in "Twelve Monkeys" - and eerily presaging a famous line from "The Sixth Sense," released a few years later.)

- "Everything will be different in the morning." (Speaking words of wisdom in "The Sixth Sense.")

THE IMAGE DIES HARD

Five things that might surprise you about the inimitable Mr. Willis:

- He was president of his senior class in high school.

- He beat out some 3,000 other actors to win the role of David in "Moonlighting."

- He co-founded the nonprofit theater troupe A Company of Fools, based in the Wood River Valley of Idaho (where Willis also owns a bar).

- He was one of Hollywood's most famous Republicans, but now says he has left the party.

- The names of his three children - Rumer, Scout and Tallulah - do not derive from figures in the King James Bible.

Who's the new Bruce?

Now that Willis is 52 - and has been dying hard for nearly 20 years - it might be time to scout a successor.

Vin Diesel: He's already established himself as an action star - and he has the polished pate to boot.

Colin Farrell: Smart-alecky Irishman starred opposite Willis in "Hart's War," so may have learned a few Bruce Moves already.

Bruce Vilanch: Maybe he doesn't have quite the right "look." But he does have the right name. And if a tough guy like Travolta can play Edna in "Hairspray," Vilanch (who also played Edna) could play a tough guy like John McClane.

The puppet Nicky from "Avenue Q": Simply because we'd love to see "Die Hard" go to Broadway.

BRUCES THROUGH HISTORY

Squint a bit and you might see a little Willis in these people from the past - both fictional and real.

Genghis Khan: Pretty tough guy, known for his wits and strategic smarts. Probably would've dabbled in Mongol community theater if not so busy conquering much of Asia.

Don Juan: He's a cad who gets around, and doesn't express a lot of regrets. Could've been the model for Willis' character in "Moonlighting."

Rasputin: Not always the sweetest guy, but had a certain charm (and a somewhat murky personal life).